Skin biopsies of rhSCF-injected test sites from patients who had received rhSCF for 1 day (A; obtained 1 hour 40 minutes after the SC injection of 5 μg/kg of rhSCF in patient no. 2) or 6 days (B; obtained 2.5 hours after the SC injection of 25 μg/kg of rhSCF in patient no. 3) show DAO-gold staining of collagen (A) that is largely abrogated by absorption of the DAO-gold with histamine before staining (B). Original magnifications (A) ×31,000; and (B) ×38,500.